Hardened Low Back Reflection Optical Fiber Physical Contacts and Connectors Containing Such Contacts and Method for Making the Same

ABSTRACT

A fiber optic connector for use with a fiber optic network having at least one predetermined operating wavelength is provided. First housing contains at least one optical fiber. The optical fiber has a free end forming a physical contact. The physical contact is coated with a protective film. The optical thickness of the protective film is at least 0.10 of the operating wavelength of the fiber optic network. Preferably, the physical contact is thermally shaped. Also preferably, the optical fiber is attached to a quick connect device forming a termini. The physical contact of the optical fiber can be readily coated with the protective film by placing the termini in a vacuum chamber.

RELATIONSHIP TO PRIOR APPLICATION

This is a U.S. non-provisional application relating to and claiming thebenefit of U.S. Provisional Patent Application Ser. No. 61/252,197,filed Oct. 16, 2009.

BACKGROUND OF THE INVENTION

Physical contact optical fiber connectors are widely used in thecommunication industry. These connectors have one or more optical fiberphysical contacts which are supported by ferrules which also physicallyalign the contacts. These optical fiber physical contacts are oftenformed by polishing the end face of the optical fiber to a preciseradius of curvature. A connector actually includes two connector halveswhich are intermatable. However, a connector half is often simplyreferred to as a connector. Thus, the single or multiple contacts areactually received within a connector half. When a correspondingconnector half containing fibers and contacts are mated with the otherconnector half, the optical fiber contacts are brought together at theirrespective radii of curvature. If the intermated surfaces of the opticalcontacts are clean and undamaged, the contacts should have reasonablylow insertion loss and small back reflection. In addition, it isimportant to correctly match these intermated optical contacts; forexample, the corresponding intermated contacts must be correctly sizedand aligned. Ideally, two fibers should be optically and physicallyidentical and held by a connector that aligns the fibers precisely sothat the interconnection does not exhibit any influence on the lightpropagation there through. This ideal situation is impractical becauseof many reasons, including fiber properties and tolerances in theconnector.

The ends of the fibers or contacts have been prepared by severalmethods, including scoring and breaking the fibers, as well as polishingthe ends. Optical fiber connector contacts having very low backreflection become more important at higher data rates. The currentpractice to obtain low back reflection is to angle polish the physicalcontact. However, because of this angle, the connector must be keyed tohave the proper orientation to mate with its correspondingangle-polished contact.

SUMMARY OF THE INVENTION

In accordance with one form of this invention, there is provided a fiberoptic connector for use with a fiber optic network having at least onepredetermined operating wavelength. A first housing containing at leastone optical fiber is provided. The optical fiber has a free end forminga physical contact. The physical contact is coated with a protectivefilm. The optical thickness of the protective film is at least 0.10 ofthe operating wavelength of the fiber optic network.

In accordance with another form of this invention, there is provided afiber optic connector for use with a fiber optic network having at leastone predetermined operating wavelength including a first housing. Thefirst housing contains at least one optical fiber. The optical fiber hasa free end forming a physical contact. The physical contact is thermallyshaped. The thermally shaped terminus is coated with a thin protectivefilm. The optical thickness of the film is less than twice the operatingwavelength of the fiber optic network, but is at least 0.10 of theoperating wavelength.

In accordance with yet another form of this invention, there is provideda method for manufacturing a fiber optic connector including providing alength of at least one optical fiber. The optical fiber has first andsecond free ends. The first free end forms a physical contact. A quickconnect device is attached to the optical fiber wherein the physicalcontact projects from one end of the quick connect device and a portionof the optical fiber projects from the other end of the quick connectdevice thereby forming a termini. A vacuum is applied to the termini.The physical contact is coated with a protective film while the vacuumis applied.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is set forth inthe independent claims. The invention, however, may be better understoodin reference to the accompanying drawings in which:

FIG. 1 is a simplified partial side elevational view showing two matingoptical fiber physical contacts of the subject invention.

FIG. 2 is a perspective view showing a fiber optic connector and aplurality of the fiber optic contacts of FIG. 1.

FIG. 3 is a front view of the fiber optic connector of FIG. 2.

FIG. 4 is a sectional view of the fiber optic connector of FIG. 3 takenthrough section line A-A.

FIG. 5 is a more detailed sectional view of a portion of fiber opticconnector of FIG. 4.

FIG. 6 is a perspective view showing a fiber optic termini with a quickconnect device which may be used in connection with the apparatus of thesubject invention.

FIG. 7 is a perspective view showing the quick connect device of FIG. 6having been spliced to fiber optic cable.

FIG. 8 is a perspective view showing an apparatus used in themanufacture of the optical fiber physical contacts of the subjectinvention.

FIG. 9 is a sectional view showing one of the holes in the apparatus ofFIG. 8 receiving a termini and a quick connect of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now more particularly to FIG. 1, there is provided opticalfiber 10, having core 12 and cladding 14. There is also provided opticalfiber 16, having core 18 and cladding 20. Fiber 10 is encapsulated byalignment ferrule 21 and fiber 11 is encapsulated by alignment ferrule23. As will be discussed below, optical fibers 10 and 16 are mounted incorresponding connector halves which are designed to be intermated.

Optical fiber 10 includes tip 22, which forms a physical contact.Optical fiber 16 includes tip 24, which forms a corresponding physicalcontact. These contacts 22 and 24 are preferably not angle polished, butpreferably have coating thickness adjusted for low reflection and may bethermally shaped for additional reflection reduction.

This thermal shaping may be done by various methods known to thoseskilled in the art, including the methods taught in U.S. Pat. Nos.6,413,450 and 6,738,554, both assigned to Megladon Manufacturing Group.The teachings of these two Megladon Patents are hereby incorporatedherein by reference.

Each physical contact 22 and 24 is coated with thin film 26, which ismade of a hard material, i.e., a material having a Knopp hardness whichis greater than the Knopp hardness of optical fibers. The preferredcoating material is Al₂O₃, also known as corundum. Corundum is a veryhard material, and thus resists scoring. Other hard coatings may also beused. Preferably this corundum film is thin enough so that light passingthrough is substantially unaffected, i.e., insertion losses are low butthick enough to resist scoring, and the optical thickness is adjusted sothat reflection is low. For the embodiments in which a single layer ofthe film is applied, the thickness of film 26 should be at least 0.10 ofbut less than 1.00 of the operating wavelength of the light within thefibers. For embodiments in which multiple layers of film are applied,the thickness of the film can be as high as 2.00 of the operatingwavelength of the light within the fibers.

FIG. 2 shows a plurality of optical fibers 10 having physical contacts22 all of which are mounted in connector body 28. Multi-fiber cable 30extends from the rear of connector body 28. Preferably the embodiment ofFIG. 2 utilizes quick connect optical fiber device as shown in FIG. 6which are known to those skilled in the art such as the quick connectdevices described in U.S. Patent Publication No. US2009/0060427 inventedby Wouters. The teachings of the Wouters Patent Publication are herebyincorporated herein by reference.

FIG. 6 shows termini 34 including quick connect device 37, optical fiber10 and physical contact 22, physical contact is coated at the tip bycorundum film 26. After coating, which is described below, termini 34 isplaced in connector body 28, and optical fiber 10 is spliced to acorresponding optical fiber located within cable 30 by a splicingtechnique known to those skilled in the art. A spliced cable 30/termini34 is shown in FIG. 7 with the splicing area indicated as item 35.Preferably, contact 22 has been thermally shaped, although the inventionis not limited to a thermally shaped contact.

It is preferred that corundum thin film coating 26 is applied to thecontacts in a vacuum chamber using a coating process known to thoseskilled in the art. In embodiments in which the connector is terminatedto a reel of optical fiber cable, if quick connect optical fiber terminiare not used, the reel, which can be very large depending on the lengthof the cable, must be placed within the vacuum chamber which can beimpractical and expensive. Using termini 34, individual termini may beplaced in the vacuum chamber for disposition of the corundum coatingapplication without the cable attached since the termini may be splicedonto the cable after coating of the film has taken place. A single layervacuum coating run is expensive, and there could be several layers forthe embodiment in which the film is used or an anti-reflective coatingin addition to providing the hardware discussed above. In addition, eachitem will need to be rotated inside of the vacuum chamber during thecoating process. By using the quick connect optical fiber terminiapproach, many more contacts can be coated at the same time with asingle coating run, and/or a smaller vacuum chamber may be used,resulting in a substantial money savings. If the connector is terminatedto a short patch cord(s) the quick-terminated optical fiber termini arenot needed since a short patch cord(s) will easily fit into the vacuumchamber.

During the coating process, it is important that only the tip 22 of theoptical fiber be coated since the coating materials are very expensiveand it would be wasteful to coat other parts of the termini.

FIG. 8 illustrates a plate 36 which may be used to segregate the fibertips 22 from the remainder of the termini during the coating process.Plate 36 includes a plurality of holes 38 which are adapted to receivetermini 34 so that the tip 22 projects below the bottom of plate 36 andthe remainder of the termini projects above the plate 36 as shown inFIG. 9. For illustration purposes only, a single termini is shown. Inreality, it is preferred that each hole in plate 36 receives a terminifor the sake of efficiency. Plate 36 is sized with a protective cover onthe top of the plate within the vacuum chamber such that the coatingoccurs in the bottom of the plate, and only the tips 22 are coated.Plate 36 is also rotatable so that the coating is uniform. Once the tips22 have been coated, termini 34 are removed from the plate and thus fromthe vacuum chamber and inserted into connector 28 as illustrated inFIGS. 4 and 5. Termini 34 is spliced to optical fiber 40, which isreceived within cable 30, at splice region 35 using splicing techniquesknown to those skilled in the art, including techniques described in theWouters patent publication.

The hard corundum coating can be applied onto several layers ofanti-reflective coating to also form a thicker hardened anti-reflectivecoating, which may in some instances eliminate the need for thermallyshaping the contact. In some multi-layer embodiments, the outer layermay be hard corundum and the inner layers may be made of other low orhigh index of refraction materials having hardness closer to the glassfiber. This anti-reflective coating can be used for one or multiplewavelength bands of operation, including, but not limited to, the bandscentered around 850 nm and 1,300 nm or 1,310 nm and 1,550 nm forexample. The thickness of the anti-reflective coating depends on thenumber of layers of the film which are used. For example, the thicknessmight vary between 0.10 and 2.00 times the operating wavelength.However, where thermally shaping is used, the hardened coating furtherincreases the hardness of the thermally shaped contact.

Multi fiber circular connectors, such as the one shown in FIG. 2, areoften used in harsh environments. Since such connectors must be keyed ifthe contacts are angle-polished, the contact orientations are hard tomaintain. The combination of a hardened surface, scratch resistantcontact and low back reflection without the need for keyed contactorientation is a great benefit for harsh environment multi-fibercircular connectors.

The physical contact fiber end faces described herein are axiallysymmetric, rugged and have low back reflection and may be used withsingle or multi-fiber connectors.

From the foregoing description of various embodiments of the invention,it will be apparent that many modifications may be made therein. It isunderstood that these embodiments of the invention are exemplificationsof the invention only and that the invention is not limited thereto.

1. A fiber optic connector for use with a fiber optic network having atleast one predetermined operating wavelength comprising: a firsthousing; the first housing containing at least one optical fiber; theoptical fiber having a free end forming a physical contact; the physicalcontact being coated with a protective film; and the optical thicknessof the protective film being at least 0.10 of the operating wavelengthof the fiber optic network.
 2. A fiber optic connector as set forth inclaim 1 wherein the optical thickness of the protective film is between0.25 and 1.00 of the operating wavelength.
 3. A fiber optic connector asset forth in claim 1 wherein the physical contact is thermally shaped.4. A fiber optic connector as set forth in claim 1 wherein theprotective film is primarily AL₂O₃.
 5. A fiber optic connector as setforth in claim 1 wherein the protective film is in the form of a singlelayer.
 6. A fiber optic connector as set forth in claim 1 wherein theprotective film is in the form of multiple layers.
 7. A fiber opticconnector as set forth in claim 1, further including a quick connectdevice; the physical contact projecting from one end of the quickconnect device and a portion of the optical fiber projecting from theother end of the quick connect device thereby forming a termini.
 8. Afiber optic connector for use with a fiber optic network having at leastone predetermined operating wavelength comprising: a first housing; thefirst housing containing at least one optical fiber; the optical fiberhaving a free end forming a physical contact; the physical contact beingthermally shaped; the thermally shaped terminus being coated with a thinprotective film; the optical thickness of the protective film is equalto or less than twice the operating wavelength of the fiber opticnetwork but is at least 0.10 of the operating wavelength.
 9. A fiberoptic connector as set forth in claim 8 wherein the protective film isprimarily AL₂O₃.
 10. A fiber optic connector as set forth in claim 8wherein the optical thickness of the protective film is between 0.25 and1.00 of the operating wavelength.
 11. A fiber optic connector as setforth in claim 8 wherein the protective film is in the form of a singlelayer.
 12. A fiber optic connector as set forth in claim 8 wherein theprotective film is in the form of multiple layers.
 13. A fiber opticconnector as set forth in claim 8, further including a quick connectdevice; the physical contact projecting from one end of the quickconnect device and a portion of the optical fiber projecting from theother end of the quick connect device thereby forming a termini.
 14. Amethod for manufacturing a fiber optic connector comprising: providing alength of at least one optical fiber; the optical fiber having first andsecond free ends; the first free end forming a physical contact;attaching a quick connect device to the optical fiber wherein thephysical contact projects from one end of the quick connect device and aportion of the optical fiber projects from the other end of the quickconnect device thereby forming a termini; applying a vacuum to thetermini; and coating the physical contact with a protective film whilethe vacuum is applied.
 15. A method as set forth in claim 14, furtherincluding thermally shaping the physical contact prior to theapplication of the vacuum
 16. A method as set forth in claim 14, furtherincluding isolating the physical contact from the remainder of theoptical fiber during coating.
 17. A method as set forth in claim 14,further including inserting the termini into a connector housing; andsplicing the termini to another optical fiber received in a fiber opticcable.
 18. A method as set forth in claim 14, further includingproviding a plate with protective cover received in a vacuum chamberthereby dividing the vacuum chamber into first and second compartments;inserting the termini into one of the holes so that the physical contactprojects into the first chamber; coating the physical contact in thefirst compartment.
 19. A method as set forth in claim 18, furtherincluding rotating the plate during coating.